Enter type of downtime

What causes this issue?

Please specify the type of downtime; there are two different types:
Planned downtime can be changed, added or deleted in a simulation. When
adopting the simulation into the planning version, planned downtimes
are copied from the simulation and the planned downtimes in the
planning version are deleted.
Planned downtime due to a resource breakdown cannot be changed in a
simulation. This downtime is always copied from the planning version
and put into the simulation. When the simulation is adopted, the
downtime remains the same.

Error message extract from SAP system. Copyright SAP SE.